Question: In history class, the girl to boy ratio is $6$ to $10$. If there are a total of $64$ students, how many boys are there?
A ratio of $6$ girls to $10$ boys means that a set of $16$ students will have $6$ girls and $10$ boys. A class of $64$ students has $4$ sets of $16$ students. Because we know that there are $10$ boys in each set of $16$ students, the class must have $4$ groups of $10$ boys each. There is a total of $40$ boys in history class.